Biology Reference
In-Depth Information
Chapter 12
Adhesive pili of the
chaperone-usher family
Vasilios Kalas, Ender Volkan, Scott J. Hultgren
Washington University School of Medicine, St. Louis, MO, USA
INTRODUCTION
Bacterial surface appendages are commonly divided into two categories: fla-
gellar and non-flagellar. Flagella are long, propeller-like structures that pro-
vide motility to bacteria, distinct from non-flagellar structures known as pili
or fimbriae, which are thinner, hair-like structures involved in adherence, bio-
film formation, and in the case of type IV pili, twitching motility (see Chapter
13). The first functional observation of adhesive pili may have been in 1908,
when Guyot recorded the ability of certain strains of bacteria to hemagglutinate
red blood cells (
Guyot, 1908
). Today, hemagglutination is a common assay for
detecting and measuring various types of adhesive pili (
Korhonen et al., 1984
;
Hultgren et al., 1986
;
Krasan et al., 2000
). The first images of non-flagellar sur-
face structures were made possible in the late 1940s-early 1950s by the inven-
tion of the electron microscope (
Houwink and van Iterson, 1950
;
Ottow, 1975
).
Duguid was an early pioneer in characterizing molecular features of pili and
used the word 'fimbriae' in 1955, meaning threads or fibers in Latin, to describe
the surface structures of
Escherichia coli
involved in erythrocyte agglutination
(
Duguid et al., 1955
). He went on to serologically distinguish these fibers using
different agglutination assays with erythrocytes from various species as well
as with yeast cells (
Gillies and Duguid, 1958
;
Duguid et al., 1966
). The term
'pili,' Latin for hair, was later used by Brinton in 1959 to describe non-flagellar
E. coli
surface appendages (
Brinton, 1959
). Soon thereafter, he reported the
first X-ray diffraction patterns of pili (
Brinton, 1965
). This consequently led
Salit and Gotschlich to establish pilus purification procedures, perform early
biochemical and functional characterizations, and describe the unique phenom-
enon of streaming birefringence exhibited by pili (
Salit and Gotschlich, 1977
).
In the 1980s, work by Stanley Falkow and Staffan Normark unraveled a genetic
understanding of pili (
Hull et al., 1981
;
Normark et al., 1983
), and in subsequent
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